Cut chicken breast into bite-sized pieces. Try to keep all the pieces of the same size, for even cooking.
In a bowl add buttermilk, salt, pepper, paprika and dijon mustard. Whisk it well. Add chicken pieces and mix it well. Cover and let it marinate for at least 1 hour (up to 24 hours) in the refrigerator.
Meanwhile, heat oil in a pan. Add breadcrumbs and toast it until it is crispy and nicely browned. Keep stirring it to prevent it from burning.
When the breadcrumbs cooled down a little bit, add all the spices, flower. Mix well and keep aside until use.
Preheat oven to 375 degrees F (190 Degree Celcius). Set a large wire rack on a baking sheet.
Take the marinated chicken out of the refrigerator. Let it sit on the kitchen counter and come close to room temperature.
Add beaten egg and flour to the marinated chicken and mix everything.
Spread breadcrumb mixture in a tray.
Take a few pieces of chicken at a time and arrange it in a single layer.
Using a fork toss chicken pieces and coat well with breadcrumb mixture. ( Watch video after the recipe to see how to coat chicken pieces without making your hands dirty)
Arrange the coated chicken pieces on the prepared wired rack, spaced little apart.
Bake for 12 minutes until it is crispy, cooked through and inside temp reaches 165 degrees F.
Optional - Once the nuggets are baked and still hot, I sometimes sprinkle a little Old Bay seasoning.